Built-in Mathematica Symbol

Select

Select[list, crit]
picks out all elements e_i of list for which crit[e_i] is True.

Select[list, crit, n]
picks out the first n elements for which crit[e_i] is True.

Select elements that are even:

Use a pure function to test each element:

Return only the first expression selected:

Select elements that are even:

Use a pure function to test each element:

Return only the first expression selected:

Select picks out elements for which applying the criterion explicitly yields True:

Applying the criterion to the symbolic object x does not explicitly yield True:

Select works with any head, not just List:

Select works with SparseArray objects:

The result may be a list if it is not sparse:

Select numbers up to 100 that equal 1 modulo both 3 and 5:

Select 4-tuples that read the same in reverse:

Find the first four 3x3 matrices of 0s and 1s that have determinant 1:

Select eigenvalues that lie within the unit circle:

Find built-in Mathematica objects whose names are less than 3 characters long:

Select numeric quantities from a product:

Find an approximation to

by finding the proportion of points that lie within a disk:

Select is similar to Cases except that it uses a function instead of a pattern:

Select the lists that have sum of elements less than 10:

Use Cases to get the same result: